1. Field
Aspects of the present invention relate to electronic devices, and in particular, to systems, methods and apparatus configured to reduce clock feed-through in switches.
2. Background
Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and multimedia applications and services. These systems are typically configured to support communication with multiple users by sharing the available system resources, such as designated portions of frequency spectrum. The popularity of high data-rate wireless services is increasing the demand for access to available frequency spectrum. The ability to satisfy the demand is often limited by a lack of available frequency spectrum that may be shared for reliable communications within a geographic area.
Various multiple access techniques have been standardized over time to allow multiple users within a geographic area to share access to available frequency bands designated for wireless communication. Currently available user devices, such as smart phones and tablet computing devices, are capable of operating in multiple frequency bands. For example, 3G cellular multimode, multiband devices can operate in three to four bands designated by 2.5G EDGE/GSM standards and another three to four bands designated by the 3G WCDMA/HSPA standards. In some deployments, 3GPP Long Term Evolution (LTE) and LTE-Advanced standards may support as many as eleven frequency bands.
The radio frequency (RF) switch is one of the many components that enable operation on multiple frequency bands. However, the often strict limits on peak transmission power of RF transmissions and the spurious effects caused by switching between multiple frequency bands present a number of challenges. In particular, conventional control of an RF switch can produce undesirable spurs (e.g. spurious tones) in the output signal of an RF switch. Uncorrected, these spurs may lead to violations of RF transmission regulations, which are set by various government agencies such as the U.S. Federal Communications Commission (FCC).
According to conventional solutions, clock spurs are reduced by including off-chip decoupling capacitors and large on-chip filtering networks. However, there are drawbacks to using these conventional solutions for reducing spurs. Off-chip decoupling capacitors add to the component count, cost and complexity of a device. They also occupy valuable substrate space, and thus limit the form factor of wireless devices. Large on-chip filtering networks occupy valuable chip space and can increase both electrical noise and the temperature of a chip during operation. Accordingly, there lies a challenge to reduce the impact of clock spurs caused by a switch controller used to enable switching between multiple frequency bands.